<!DOCTYPE html>
<html>
<head>
  <link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/base/jquery-ui.css" rel="stylesheet" type="text/css"/>
  <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5/jquery.min.js"></script>
  <script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/jquery-ui.min.js"></script>
  <style type="text/css">
   
 #draggable { width: 75px; height: 25px; background: silver; padding: 10px; }
        
    .Rot {
	background-color:red;
	position: absolute; 
	left: 250px; top: 0;
	width: 125px; 
	height: 75px;
	padding: 10px;
}
    
    .Blau {
	
	background-color:blue;
    position: absolute; 
	left: 250px; top: 0;
	width: 125px; 
	height: 75px;
	padding: 10px;

}
    
  </style>
  
  <script>
	$(function() {
		$( "#draggable" ).draggable();
		});
	</script>
	
	  <script>
	$(function() {
	
		$( "#droppable" ).droppable({
			drop: function( event, ui ) {
				$( this ).removeClass('Blau').addClass('Rot');   
		    }
		});
	});
	</script>

  
  
  
  
  
</head>


<body style="font-size:62.5%;">
  
<div id="droppable" class="Blau">Drop here</div>
<div id="draggable">Drag me</div>

</body>
</html>